Although spike tires have been used and chains have been loaded on tires for running on snow and ice road surface, environmental problems such as dust are generated; therefore studless tires were developed as tires for running on snow and ice road surface in place of these.
Since the snow and ice road surface is remarkably low in frictional coefficient in comparison with general road surface and tires slide easily, the devices of material viewpoint and design viewpoint are carried out. For example, a rubber composition compounding a diene rubber superior in low temperature property is developed. Further, there have been tried devices that surface edge component is increased by changing the uneven mode of tire surface and frictional performance on ice is improved by compounding inorganic fillers having scratch effect (refer to Japanese Unexamined Patent Publication No. 8-217918) to obtain the scratch effect to ice on the snow and ice road surface.
However, frictional performance on the snow and ice road surface is not adequate even by the fore-mentioned studless tires in comparison with spike tires and further improvement is desired.